We birded Glendalough State Park during the Detroit Lakes Bird Festival. There were common yellowthroats singing on territory all over. I even managed to get video of them through my spotting scope and digital camera. They are usually described as having a song that says, "witchety, witchety, witchety" but sometimes they can be a little different. Here are two different common yellowthroats singing, the first is the usual call and the second is just a little different (you can go directly to YouTube and watch them in high definition if you want):